Production of an improved non-austenitic steel weld deposit

ABSTRACT

A method of producing an improved non-austenitic steel weld deposit characterized by superior toughness in the Charpy V-notch impact test by melting a covered ferrous low hydrogen arc welding electrode consisting of a current conductive core and a limefluoride coating, which method consists of proportioning the core and coating components containing metallic and oxide forms of the basic metals of the group consisting of lithium, sodium, potassium, cesium, magnesium, calcium, strontium and barium and of the acid metals of the group consisting of aluminum and silicon so that when all components are melted together under the influence of an electric arc they produce a weld metal deposit and a welding slag with a basicity or mole ratio of oxide of basic metal to oxide of acid metal of at least 2.2 and restricting the sources of metallic and oxide forms of titanium in the core and coating components so that the weld metal deposit contains less than 0.07 percent titanium.

United States Patent 11 1 De Long et al. Oct. 30, 1973 1 PRODUCTION OFAN IMPROVED 3,153,719 10/1964 Arikawa et al. 214/146 NON AUSTENITICSTEEL WELD DEPOSIT 3,501,354 3/1970 DeLong 148/23 [75 lnventors: WilliamT. De Long; Edwin R.

Szumachowski, both of Pittsburgh, Pa.

[131 Assignee: Teledyne Inc., Los Angeles, Calif.

[22] Filed: May 6, 1971 [21] Appl. No.: 142,022

Related US. Application Data [62] Division of Ser. No. 850,631, Aug. 15,1969, Pat. No.

[52] US. Cl 219/137, 117/205, 117/206, 219/ 146 [51] Int. Cl. B2311 9/00[58] Field of Search 219/137, 145, 146; 117/202-206; 148/23-26 [56]References Cited UNITED STATES PATENTS 3,423,565 l/l969 Malchaire117/206 3,342,974 9/1967 Wallner 1'17/205 3,453,142 1/1969 Dolscau etal. 117/206 3,539,765 1l/l970 Duttera et al 214/146 2,900,490 8/1959Petrick et al. 117/206 3,211,582 10/1965 Wasserman et al... 117/2063,102,827 9/1963 Kriewair et al. 117/206 Primary Examiner-R. F. StaublyAssistant Examiner-George A. Montanye Attorney-Edward Hoopes, Ill

[57] ABSTRACT A method of producing an improved non-austenitic steelweld deposit characterized by superior toughness in the Charpy V-notchimpact test by melting a covered ferrous low hydrogen arc weldingelectrode consisting of a current conductive core and a limefluoridecoating, which method consists of proportioning the core and coatingcomponents containing metallic and oxide forms of the basic metals ofthe group consisting of lithium, sodium, potassium, cesium, magnesium,calcium, strontium and barium and of the acid metals of the groupconsisting of aluminum and silicon so that when all components aremelted together under the influence of an electric are they produce aweld metal deposit and a welding slag with a basicity or mole ratio ofoxide of basic metal to oxide of acid metal of at least 2.2 andrestricting the sources of me- 18 Claims, N0 Drawings PRODUCTION OF ANIMPROVED NON-AUSTENITIC STEEL WELD DEPOSIT This application is adivision of my copending application Ser. No. 850,63 l filed Aug. l5,1969, now US.

are covered by the three AWS classes E-XXIS, E- XXl8 and E-XX28. Ofthese three classes, the E-XXIS may be considered the base, the othertwo in effect representing progressive transfer of metal from the Pat.No. 3,627,574. core to the covering. The tabulation below lists the Thisinvention relates to the production of weld defunctional componentscontained in lime-fluoride low posits by improved lime-fluorideelectrodes with coathydrogen electrodes of the three AWS classes and theings of the type known as low hydrogen and classinormal limits of eachcomponent, expressed in per fied by the American Welding Sciety intheclasses E- cent. by weight of the electrode, in finish-baked elec-XXl5, E-XX18 and E-XX28, which are especially l0 trodes of each class.

Percent Slag Alloying Deoxldizer Alkaline builder metal metal Metalearth and Inorganic AWS Class Core powder powder fluoride carbonatemodifier binder E-XX 70-80 0-5 2-7 4-15 5-15 0-10 0. 6-8 EXX18 55-725-15 2-1 4-15 5-15 0-10 05-8 E-XX28 45-55 20-30 2-7 4-15 5-15 0-10 0.5-8

suited to produce non-austenitic steel weld metal hav- 20 The E-XX18,which is the most popular class, is used ing unprecedentedly improvedtoughness as measured to illustrate our invention, although theinvention is not by the Charpy V-notch impact test without sacrifices inlimited to that class. By virtue of the fact that the othercharacteristics such as electrode weldability or greatly improvedelectrodes of our invention are of the deposit strength, ductility andcrack resistance. lime-fluoride low hydrogen type, they too contain theIn the production of weld deposits by means of limeab v d rib d n e aryfunctional components fluoride low hydrogen electrodes, prior workershave common to all electrodes of this type. developed many conceptswhich are generally em- The weld metal deoxidation level ofnon-austenitic ployed in such electrodes throughout the weldinginlime-fluoride electrodes, measured primarily by the silidustry. Whileour invention teaches important new 'adcon level recovered in thedeposit, is customarily advances in the art it does not'obviate the needto con- 0 ju'sted through additions of deoxidizer metal powder to tinuethese well established principles to produce satisthe coating to providea good balance between soundfactory welding electrodes. Since knowledgeof this ness and mechanical properties in the weld metal. A prior art ispertinent to a clear understanding of our indeposit silicon below about0.25 percent is usually detvention, certain of it is reviewed here,primarily with rimental to both impact strength and welding operarespectto securing deposit toughness or impact tion. The optimum silicon levelis usually between strength. In addition, since the chemical compositionof about 3 percent d 5 percent, d di somethe resultant welding slagproduced by our limewhat on the overall deposit analysis; as the depositsilifluoride electrode is importantly related to the descrip conincreases above 0.5 percent, welding operation tion of our invention,some aspects of the present state usually remains good or may evenimprove, but the deof the art with respect to lime-fluoride electrodecoat- 40 posit impact strength generally deteriorates. Deoxiing andwelding slag terminology are presented. dizer metals in the coating orcore react with available As the commonly used term lime-fluoride lowhycarbon dioxide from carbonate in the coating or with drogen electrodeindicates, the coatings of such elecoxygen from the air to produceoxides which go into trodes have very low moisture content and containas the slag. Strong deoxidizers, for example aluminum, titheir principalfunctional ingredients alkaline earth cartanium, zirconium and the rareearth metals, are almost bonate, usually calcium carbonate, and metalfluoride, completely oxidized unless they are present in large usuallycalcium fluoride. Through the manipulation of amounts; under favorableconditions small proportions these and other coating ingredientsincluding slag of these do go into the weld metal. Weaker deoxidizersbuilders and modifiers such as silicates and oxides, desuch as siliconand manganese tend to go more equitaoxidizer metal powder such assilicon, manganese, alubly to the slag as oxides and to the weld metalas alloyminum, etc., alloying metal powder and inorganic ing elements.binder material, coating formulators have been able to The slagcomposition produced by a covered arc obtain electrodeswhich producewelding slag composiwelding electrode is a product of the reactionswhich tions having the proper melting point, viscosity, wetting occurbetween the metallic core, flux coating materials behavior, operatorappeal, etc. Typically such limeand are atmosphere during welding.Certain welding fluoride low hydrogen electrodes produce welding slagsslags are described as acid, while other slags, such as containing notless than 20 percent of fluoride, with those produced by lime-fluoridewelding electrodes, about 30 percent to percent fluoride being common.are termed basic. Depending upon the source, the Adequate protective COgas to shield the are from ni- 60 imprecise term basic means that theratio, expressed trogen of the air is supplied through the thermal deinpercent or in moles, between the oxide content in the composition of thecarbonate in the coating during slag of metals considered basic and thatof metals conwelding. In addition to supplying CO the carbonate sideredacid is greater than one. In our work we define supplies oxide to theslag. Care is exercised in selecting lithium, sodium, potassium, cesium,magnesium, calnon-hygroscopic ingredients low in water content for cium,strontium and barium as basic metals and silicon the coating; a finalhigh baking temperature insures a coating of low total moisture content.

Commercially successful lime-fluoride low hydrogen electrodes producingnon-austenitic steel weld deposits and aluminum as acid metals. Othercommonly employed oxides such as titanium oxide and salts such asfluorides are considered neutral in their effect on slag basicity, whichwe define as the ratio of moles of oxide of basic metal to moles ofoxide of acid metal present in the slag. Using our definitions,successful limefluoride electrodes of the prior art have produced slagshaving basicities ranging from about 1.2 to about 1.9.

The basicity of a lime-fluoride low hydrogen welding 5 slag compositionmay either be determined directly from its chemical analysis or beclosely approximated by a slag basicity calculation. The latter methodrequires a knowledge both of the compositions of the weld deposit andthe metallic core of the electrode and of the flux materials and howthey behave in the welding process; it can best be described by carryingout one such basicity calculation for an AWS E-70l8 type low hydrogencovered electrode typical of the prior art. in this example a 5/32 inchdiameter mild steel core wire was extrusion coated with a coatingmixture comprising the ingredients and amounts shown in Table l. Thefinished electrode contained about 35 percent coveringandabout 65percent core by weight. From the chemistry of the deposit and thechemistry of the core 1 wire it .can be determined what metal wasoxidized and what was recovered; knowing this and the compositions andweights of the coating ingredients and ignoring the small fume losses,the amounts of oxides of acid and basic metals in the slag compositionwhich are of special interest can be calculated as shown in Table l. Thetotal moles of oxides of basic and acid metals are 0.285 and 0.206respectively for this example, and they are then used to calculate thebase-to-acid mole ratio or slag basicity, which is 1.38.

Iron powder Sodium bicarbonate Wollastonite Total dry materials Mixedalkali silicate binder 21cc 6.14 1.81 1.47 Totaloxldes 11.54 1.36 12.613.08 1.61

Acid Acid Base Base Base NOTE.-

Total base in moles Total acid in moies .206

As previously indicated, successful lime-fluoride low hydrogenelectrodes of the prior art have produced slag basicities in the rangeof about 1.2 to about 1.9. This range of values has been promotedbyseveral factors. 'The silicate binder contributesan appreciable amountof silica, and the conventional ferro-silicon deoxidation, which iseffective, cheap and convenient, contributes more. The alkali oxides NaO and K 0 are limited in quantity partly because of their effect onoperation and partly because it is difficult to obtain materials rich inthese oxides yet with low water content and low tendency to rehydrate.The calcium carbonate can be increased, but the increased carbon dioxidethus generated requires a corresponding increase in deoxidation, usuallythrough an increase in ferrosilicon, which adds more acid oxide to theslag. Sometimes aluminum may be used for deoxidation, but its oxideresidue is also acid in the slag. Thus it can be seen that lime-fluoridelow hydrogen electrodes of the prior art have had their slag basicitiesdepressed by conventional practices in the areas of binder anddeoxidation; in the few cases where basicity has been raised, thepotential benefits to the produced weld deposits have been largelydissipated by the immoderate use of titanium.

As modifiers for controlling and adjusting the properties oflime-fluoride welding'slags, the oxides of aluminum, titanium andzirconium have been commonly employed. They may be introduced into theslag melt via the electrode either as the oxides or in equivalent forms,e.g., associated with another oxide as oxide of titanium is in potassiumtitanate. Note the example in Table 1. Typical ranges for thesemodifiers have been up to 8 percent alumina, up to 12 percent zirconiaand up to 15 percent titania by weight of theslag. If introduced in somemetallic form for deoxidation purposes, after the metals have servedthis function their oxide residues appear in the slag where they exerttheir usual.

effects. I

The effects of the metals aluminum, titanium and zirconium on themechanical properties of the weld deposit have in the past beenassociated with deoxidation, denitrification and with small alloyingconcentrations, particularly of titanium, recovered in the deposit.

When a lime-fluoride electrode composition provides the setting for theuse of these strong'deoxidizer metals the efficiency of recovery varieswith position in the electrode, a coating position being less efficientthan one in the core which is more protected during arc transfer.

For some time it has beenapparent that all prior art lime-fluoride lowhydrogen covered electrode compositions, even though including the mostskillful combinations of deoxidizers, have become virtually stalled intheir progress toward further significant improvements in the impactresistance of non-austenitic steel weld metals; moreover, the best welddeposits produced with prior art electrodes of this type have often beeninadequate or marginally acceptable in impact strength and thusrestricted to the less critical applications. Some deposits, such as the2 1% percent and 3 7% percent nickel types, are often marginal intoughness at -l50F.' when produced by downhand welding and are notacceptable when produced by vertical welding; comparable plate materialsare satisfactory at l50F. 9 percent nickel ferritic covered electrodesproducing deposits which match 9 percent nickel plate in toughness at320F. have been unavailable. Higher strength weld deposits, such asthose produced with the best currently available E-l40l8 electrodes foruse with tough wrought steels having ksi minimum yield strength, havebeen marginal in toughness. The toughness of low alloy Cr-Mo deposits,e.g., those from AWS E-901 8B3 electrodes, should be better to minimizethe risks of brittle failure. Heat-treatable or stressrelievabledeposits with strength and toughness both at desired high levels areoften not available.

In view of the above described situation, it can be seen that there hasbeen a clear and pressing need for covered electrodes which can producenon-austenitic steel weld metal with superior toughness withoutsacrificing weldability, strength, ductility, crack resistance or otherdesirable properties.

We have found that improved non-austenitic steel weld deposits withsuperior toughness can be produced with low hydrogen lime-fluoridecovered electrodes by combining proper deoxidation practices with newapproaches to welding slag composition which are inherently favorableto' high impact strength. Additional benefits may be obtained byemploying titanium in various forms in the electrode according to ourdirections.

We provide a covered ferrous low hydrogen arc welding electrode of theclass wherein a current conductive core is covered with a lime fluoridecoating, the electrode containing by weight about 45 percent to about 80percent core and about 20 percent to about 55 percent coating, thecoating containing by weight of the electrode to about 30 percentalloying metal powder, about 2 percent to about 7 percent deoxidizermetal powder, about 4 percent to about 15 percent metal fluoride, about5 percent to about percent alkaline earth carbonate, 0 to about 10percent slag builder and modifier and about 0.5 percent to about 8percent inorganic binder material, the electrode producing anon-austenitic steel weld metal deposit characterized by superiortoughness in the Charpy V-notch impact test, the electrode containingbase components selected ,from metallic and oxide forms of basic metalsof the group consisting of lithium, sodium, potassium, cesium,magnesium, calcium, strontium and barium and acid components selectedfrom metallic and oxide forms of acid metals of the group consisting ofaluminum and silicon, said base components and acid components being soproportioned that when all components are melted together under theinfluence of an electric welding arc the electrode produces a weldingslag with a basicity or mole ratio of oxide of basic metal to oxide ofacid metal of at least 2.2, and preferably at least 3, the electrodebeing restricted in sources of metallic and oxide forms of titanium sothat when all components are melted together under the influence of anelectric welding arc the electrode produces a weld metal depositcontaining less than 0.07 percent titanium, and preferably less than0.045 percent titanium.

We also provide a method of producing an improved non-austenitic steelweld deposit characterized by superior toughness in the Charpy V-notchimpact test by melting a covered ferrous low hydrogen arc weldingelectrode consisting of a current conductive core and a lime-fluoridecoating, which method consists of proportioning the core and coatingcomponents containing metallic and oxide forms of the basic metalslithium, sodium, potassium, cesium, magnesium, calcium, strontium andbarium and of the acid metals aluminium and silicon so that when allcomponents are melted together under the influence of an electricwelding arc they produce a weld metal deposit and a welding slag with abasicity or mole ratio of oxide of basic metal to oxide of acid metal ofat least 2.2, and preferably at least 3, and restricting the sources ofmetallic and oxide forms of titanium in the electrode so that the weldmetal deposit contains less than 0.07 percent titanium, and preferablyless than 0.045 percent titanium.

We further provide in preferred embodiments of the invention that thehigh slag basicity is promoted by supplying part or all of the requiredelectrode deoxidation by magnesium in metallic form.

We further provide in other preferred embodiments of the inventionlimits described hereinafter on the presence of titanium as oxide andmetallic titanium in improved lime-fluoride electrodes of the inventionin order to control and tomaximize toughness in the weld deposit.

We further provide in other embodiments of the invention that thecurrent conductive core of the electrode may be of commercial mildsteel.

Our improved electrode produces unprecedentedly tougher weld depositsthan have heretofore been available from the best lime-fluoride lowhydrogen covered electrodes. The degree of improvement depends upon thealloy system used, some alloy systems showing much more improvement thanothers as our examples will demonstrate. With a given alloy system theadvantages are obtained to a lesser degree as the outer limits of theinvention are approached. The typical maximum degree of improvementvaries in general from about thirty per cent. to several hundred percent. Covered electrodes have heretofore been regarded as having lesspotential than either gas metal arc or gas tungsten arc weldingprocesses, based on the previously attainable deposit toughness. Themajor improvement in deposit toughness obtained with our invention,coupled with availability of welders-skilled in the shielded arc processand the general case of use, dependability and low cost of coveredelectrodes makes such electrodes leading contenders for the high qualityapplications where they have been lagging or are being phased out.

Other details, objects and advantages of the invention will becomeapparent as the following description of certain present preferredembodiments thereof and certain present preferred methods of practicingthe same proceeds.

EXAMPLE 1 An AWS E-l 1018 type electrode was prepared from the followingflux composition, which was applied to a standard commercial quality5/32 inch diameter C-l008 mild steel conductive core wire and then bakedto a low water content. The covering comprised about 35 percent of theelectrode weight and contained sufficient alloy to meet the E-l1018deposit strength requirements.

Dry ingredients grams Calcium carbonate 200 Calcium fluoride 43.3Magnesium metal 2.7 50% ferro silicon 5.0 40% ferro titanium 0.13 Nickel4 37 65% ferro molybdenum 1.5 lron powder 19.3 Manganese metal 3.7

Total dry ingredients 100.0

Wet ingredients (binder) Water 1 1.90 Organic extrusion aid 1.52Potassium hydroxide 0.67 Sodium aluminate (40% 1.91 sodium oxide, 31%aluminium oxide, 23% water) Total wet ingredients 16.00

This electrode used a sodium aluminate binder of the type described incopen ding application Ser. No. 706,681, filed Feb. 19, 1968, now U. S.Pat. No.

A calculation similar to that shown in Table I shows that this electrodeproduces a welding slag with the unprecedentedly high basicity of 4.42;the greatly im-. proved impact properties of the metal which it depositsare shown in Table 11 where they are compared with those of anessentially equivalent deposit representative of the prior art.

TABLE II Prior Art lnvention E1 1018 Example 1 Electrode slag basicity1.48 4.42 Hardness, Rockwell C'Scale 29 33 Charpy V-notch, ft-lbs Roomtemperature 85 143 100 F. 39 77 150 F. 8 43 Deposit Chemistry, Carbon0.086 0.092 Manganese 1.55 1.81 Silicon 0.40 0.36 Nickel 1.6 1.76Chromium 0.4 0.36 Titanium 0.045" 0.045"

d derived from alloy recovery curves The alloy content of the welddeposit of Example 1 happens to be slightly higher than the prior art E11018 deposit and therefore is of somewhat higher hardness. This increasein hardness would be expected to reduce the impact strength, but it canbe seen that our invention brings about substantial increases in impactstrength, on the order of from 68 percent to over 400 percent dependingon the testing temperature. Of particular importance is the fact thatour invention may employ standard commercial quality core wire and doesnot require the use of expensive high purity wires.

EXAMPLE 2 A second electrode of our invention was prepared using thefollowing flux composition, which was applied to a standard commercialquality 5/32 inch diameter C-l008' mild steel core wire and then bakedto a low water content. The coating comprised about 35 percent of theelectrode weight and contained sufficient alloy to produce a 3 6 percentnickel low alloy type deposit.

A calculation for this electrode shows a welding slag basicity of 2.59.

Listed in Table 111 are comparative data on the deposit of this new 3'16 percent nickel electrode and that of a representative prior artelectrode.

TABLE [11 Y Prior Art Example 2 Electrode slag basicity 1.48 2.59Hardness, Rockwell C Scale 21 20 Charpy V-noteh, ft-lbs Room Temperature146 161 F. 54 I01 150 F. 22 38 Deposit Chemistry, Carbon 0.059 0.073Manganese 0.67 0.66 Silicon 0.33 0.41 Nickel 2.98 3.0 Titanium 0.045"0.()45

d derived from alloy recovery curves Example 2 shows a distinctimprovement in deposit toughness over the prior art, especially at lowtemperatures, in spite of only a modest elevation of slag basicity to2.59.

- As Examples 1 and 2 respectively illustrate, the improved electrodesof our invention may have a coating bonded with an alkali aluminate oran alkali silicate. Both Examples 1 and 2 also illustrate successfulembodiments of our invention which employ a wellbalanced group ofdeoxidizer metals, one of which, metallic magnesium, is a convenient andpractical deoxidizer whose oxide residue importantly serves to increasethe basicity of the welding slag. 1n the coating of Example 2, if thetwo grams of metallic magnesium were to be replaced by 2 grams of 50percent ferrosilicon the slag basicity ratio would be reduced from 2.59to 1.70, which is no higher than that of typical prior art electrodes.In the coating of Example 1 with an aluminate hinder, the effect issimilar. Use of 2.7 grams of magnesium instead of 2.7 grams of 50percent ferrosilicon, in conjunction with the substitution of analuminate binder for conventional silicate binder, has increased theslag basicity from about 1.75 to the 4.42 value shown. In Example 1, ifmagnesium were not used to carry a substantial portion of thedeoxidation load, i.e.,if ferrosilicon alone were used, the basicity ofthe slag would approximate our broad lower limit of 2.2 minimum butwould not exceed the preferred lower limit of 3 minimum required by ourinvention. With the use of magnesium the desired minimum basicities arereadily exceeded.

EXAMPLE 3 A third electrode of our invention was prepared using acoating similar to Example lbut with a higher calcium carbonate leveland other minor changes. The covering, listed below, comprised about 35percent of the electrode weight and contained sufficient alloy to meetE-l40l8 deposit strength requirements.

I grams Calcium carbonate 29.9 Calcium fluoride 29 3 Magnesium metal 50%ferro silicon Rutile Nickel 65% ferromolybdenum 70% ferrochromiumManganese metal lron powder Manganese oxide CMC (extrusion aid) Totaldry materials The binder was like that of Example 1 but without thepotassium hydroxide.

The greatly improved impact properties of this E-14018 weld metal overtypical prior art E-14018 weld metal are shown in Table IV.

TABLE IV Prior art Invention 14018 Example 3 Electrode slag basicity 1.54.5 Hardness, Rockwell C Scale 37 37 Charpy V-notch, ft-lbs RoomTemperature 50 79 F. 73 60 F. 35 60 Strength Ultimate strength, ksi 147159 Yield strength, ksi 141 142 Elongation, 18 19 Deposit Chemistry,Carbon 0.08 0.074 Manganese 1.90 1.77 Phosphorus 0.006 0.004 Sulfur0.005 0.003 Silicon 0.43 0.41 Chromium 0.55 0.78 Nickel 2.00 2.59Molybdenum 0.42 0.49 Titanium 0.045 0.045 a average of tests in a seriesof experiments d derived from alloy recovery curves tively, than thatfrom the low basic prior art electrode.

1n the absence of metallic magnesium, other modifications may be made tothe coating of our electrodes to raise the slag basicity. One suchmodification is the use of stable forms of magnesium oxide- Others mayinclude reduction of the binder silica content by using lower amounts ofbinder or diluted binder, further increase in the alkali level throughthe use of hydroxides, carbonates or titanates within permissiblelimits, substitution of other de'oxidizers for silicon, such as calcium,lithium (although these two metals pose problems due to reactivity withthe binder, as is understood by those skilled in the art), titanium(within the limitations imposed by its effect on impact properties) orthe rare earth metal family (mischmetal) to a limited extent, and otherexpedients. With the use of combinations of these techniques, the slagbasicity produced by a limefluoride electrode can be increased above ourbroad limit of 2.2 into more favorable areas than have heretofore beencommonly used in the art, bearing in mind that commercial standards ofcoating toughness and electrode operation must be maintained. The use ofmetallic magnesium makes the attainment of favorable slag basicity mucheasier than the use of some of the alternatives described.

Past investigators have recognized that the use of the metals titanium,aluminum and zirconium in wires for gas shielded or submerged arcwelding has influenced the impact strength of the weld metals. However,we found that the lime-fluoride covered electrodes titanium is the mosteffective in influencing weld toughness, with aluminum and zirconium ofonly secondary interest provided an excess is avoided, e.g.,we.havefound a weld deposit aluminum content greater than about 0.03 percent tobe harmful. We provide for limitations on the amount of titanium inthemetallic and oxide form in the improved lime-fluoride electrodes of ourinvention, such limitations being dependent upon both the amount ofcarbon dioxide released by the coating and the basicity of the weldingslag produced. In the predominantly carbon dioxide atmosphere derivedfrom the carbonate content of the electrode coating, a metallic form oftitanium would be expected to oxidize readily and to be scarcelyrecovered in the weld; even less expected would be the reduction oftitanium oxide. 1n the welding field experts in the prior art havevariously regarded titanium dioxide to be acidic, amphoteric or neutralin the slag. 1f acidic or amphoteric, it would be expected to be moreclosely and readily held in a highly basic slag than in a more acidslag; thus the amount of titanium in the weld metal in equilibrium witha given amount of titanium dioxide in the slag would be expected todecrease as the basicity of the slag increased (the equilibrium betweensilicon in weld metal and silicon dioxide in the slag behaves in thismanner). Unexpectedly, the reverse has been found to be true, i.e., asthe basicity of the slag increases the amount of titanium recovered inthe weld metal increases for a given amount of titanium either as metalor as oxide present in the electrode.

Examples of improved impact strengths attainable through the controlleduse of titanium in various common forms are shown in Table V, whichlists test results for deposits from a series of 5/32 inch 10018 typeelectrodes producing a slag basicity of about 4.5 and made approximatelyas the electrode of Example 1. All electrodes carried requisiteadditions of alloy; Examples 5, 6 and 7 embody additions of optimumamounts of titanium in different forms to the coating of Example 4, thetitanium-free base composition of the series. All electrodes were testedunder standard conditions and produced deposits with a hardness of about25 Re, a yield strength of about 90,000 psi and a deposit chemistry ofabout 0.07 percent carbon, 1.1 percent manganese, 0.4 percent silicon,1.7 percent nickel, 0.4 percent chromium and 0.3 percent molybdenum.

TABLE V Example 4 5 6 7 Potas- 42% Description Base, no sium TiOferrotitanium titanate pigment titanium 111 any form Grams added to noadcoating dition 1 .67 1.0 0. 12 Available titanium, of electrode wt. 00.26 0.21 0.0176 Titanium in deposit Nil 0.024 0.02 0.003

No. of test plates run 3 2 1 2 Average Charpy V-notch energy absorption,ft-lbs: Room temperature 180 250 224 197 F. 70 115+ 111+ 102+ F. 25 2416 39 d derived from alloy recovcurves Note: The plus sign after some ofthe values indicates that one of the bars tested at that temperatureexceeded the 118 ft'lb capacity of the impact test machine. Since a widespread in values is common in impact testing the average of severaltests is customarily used.

The impact test results for the deposit of Example 4, the basecomposition, are far superior to those from prior art deposits of equalstrength level. The toughness of the base can be still further increasedby optimum a 1 1 levels of titanium added in various forms, as shown bythe test results of Examples 5, 6 and 7.

Similarseries of tests were run at slag basicity levels of about 1.79,2.44 and 3.9 and also at two carbon dioxide levels for each slagbasicity Q supplied respectively by and 30 grams of calcium carbonateper 100 grams of coating. The weld metal deoxidation level wasmaintained-about the optimum point by adjusting the electrode deoxidizercontents slightly for changes in the carbonate content or for theaddition of metallic titanium; although the strength levels changedsomewhat with small variations in carbon and manganese recovery it wasstill possible to organize the data from these test series to find inbroad terms the optimum electrode titanium additions as well as themaximum titanium which could be used with benefit in electrodes of ourinvention. j

' By organizing and plotting the test results from many E-XX18 typeelectrodes we have found that to be able to knowledgeably manage'thequantities of titanium supplied from various sources in the electrode itis necessary to take into acount (1) the electrode slag basicity, (2)the quantity of carbon dioxide generated by the coating and (3) thelocation and form of the titanium present, metallic titanium in thecorebeing more efficient than metallic titanium in the fiux coating which inturn is more efficient than titanium in oxide form in the flux.

With respect to improved electrodes of our invention which produce basicslags we will now show (1) how highj thetitanium may go before depositimpact values have fallen back from the optimum to values equal tothose'of the startingpoint, (2) how titanium may be used to produceoptimum impact improvements and (3) to aboutwhat levels the deposittitanium must be restricted to keep the deposit impact values abovethose characteristic of prior art deposits. in setting forth therelationships for controlling titanium, average welding conditions areassumed, all percentages are given in terms of electrode weight and thefollo wing terms are employed: I

percent electrode titanium as oxide present in the coating percentelectrode titanium as metal present in the coating percent electrode COpresent in the coating; derived from carbonate, for example calciumcarbonate. I

As above stated, impact testing of many series of E- XX18 electrodedeposits made with ourv improved lime-fluoride electrodes has shown thatthe most successful use of our invention requires the management oftitanium; from analysis of test data, limitations on the use of titaniumhave been generally determined. The data of Table Vi, secured byconstructing curves for each series of an experimental electrodeprogram, shows a direct relationship to exist between slag basicity andthe maximum amount'of titanium in oxide or metallic form which can beadded with benefit to the coating of a, titanium-free base composition.With graphical aid Table VI was generalizedinto Table Vl-A, which showsthat in respect to the stated effect on deposit impact strength 1percent electrode titanium as metal present in the coating is about 2.6times as effective as 1 percent electrode titanium as oxide present inthe coatin't. The factor 2.6, although only approximately correct overthe range of slag basicities employed in the practice of our invention,serves as a practical factor to combine in one expression the effect oftitanium when present in both the oxide and the metallic forms. TableVI] shows the relationship between slag basicity and the maximum valuefor an expression providing for the presence of titanium in both oxideand metallic forms in the coating. Electrodes made with the maximumcontents permitted produce deposits containing about 0.03 percenttitanium.

A different principle applies to the limits on the level of titaniumrequired to produce the optimum improvement in deposit impact propertiesat temperatures from 60 F. to 1 50 F. for the low alloy high strengthelectrodes of the Ni-Cr-Mo varieties and the nickel-bearing grades asrepresented by the 3 1% Ni type.

The set of tests which produced the data of Table VI also produced thedata of Table V111, which relates optimum ranges of quantities offlux-borne titanium present in the electrode to percent electrode COpresent in the coating rather than to slag basicity. As columns A and Bof this table show, when titanium as oxide is the only titanium sourcethe optimum range for percent electrode titanium as oxide present in thecoating/percent electrode 10 present in the coating is 0.039 to 0.133,and when titanium as metal is the only source the optimum range forpercent electrode titanium as metal present in the coating/percentelectrode CO present in the coating is 0.0037 to 0.0116.

A comparison of these two expressions shows that, with respect to theoptimum improvement of impact values, titanium in the metallic form isabout 11 times as effective as it is in the oxide form when either isadded through the coating. This factor of about 1 1 serves practicallyin combining in one expression the effects of titanium when present inboth the oxide and metallic forms. in respect to optimum low temperatureimpact improvement a value of about 0.04 to about 0.13 is optimum forthe expression (percent electrode titanium as oxide present in thecoating 1- 11 times percent electrode titanium as metal present in thecoating/percent electrode CO present in the coating) 7 TABLE VI TABLEVI-A percent Electrode Electrode titanium as titanium as oxide metalAvg. ratio, Slag basicity (Column A) (ColumnB) Col. A/Col. B

1 2. 50 1 Average.

TABLE VII Maximum value for expression percent electrode titanium asoxide present in the coating plus 2.6 times percent electrodetitanium asmetal present Slag basicity range in the coating" to produce improvementover base Less than 3 1. 71 3-4 1.18 Over 4 80 Table lX -(ontinued' b.11 times electrode titanium as metal present in the coating/76 electrodeC0,

present in the coating 0.02 0.07 (a) plus (b) (which must lie between0.04 and Metallic elements recoverable in the deposit may either bepresent in the flux coating of the electrode or be alloyed or enclosedin the conductive core. This is true of metallic titanium in improvedlime-fluoride electrodes of our invention, but the use of specialanalysis titanium-bearing core instead of plain mild steel, whiletechnically feasible, greatly increases the cost of the electrodeswithout returning any significant advantage. There is some slightcompensation in the fact that metallic titanium in the coating may bereplaced by about one-fourth less titanium in the core because of themore protected position and improved efficiency of recovery; this factormay be checked by a few tests in TABLE viii-RANGES OF TITANIUM PRESENTIN THE COATING EITHER AS OXIDE OR AS METAL'TO PRODUCE OPTIMUM LOWTEMPERATURE IMPACT IMPROVEMENT Percent Grants Electrode ElectrodeElectrode Electrode Electrode titanium as titanium as 0:100; 00;COzprestitanium as titanium as oxide, metal,

in the in the in the oxide present metal present percent 002 percent CO2Avg. ratio, Slag basielty coating coating coating in the coating in thecoating (Col. A) (001. B) Col. A/Col. B

039-. 133- 0037-. 0116 l No data. 2 Average.

' It is well known to those familiar with the state of the coveredelectrode art that some forms of titanium dioxide in the coating,preferably titanium dioxide pigment but sometimes rutile or potassiumtitanate, are beneficial to operator appeal. While titanium dioxide isdesirable from this viewpoint and does help impact values when used inthe proportions we have defined, the beneficia] effects which it conferson deposit toughnessare not quite as strong at the lowest testtemperatures as those conferred by metallic sources of titanium.However, if only metallic titanium is used in the coating, the optimumlevel is so low that the amount of titanium dioxide obtained from theoxidation of the excess titanium is insufficient to have the desiredbeneficial effect on operation. We have found that it is usuallydesirable to balance the coating to obtain as much as practical of thedesired effect of titanium dioxide as an operation improver and some ofthe effect of metallic titanium as the preferred low temperaturetoughness improver by combining the two in the coating as shown in TableIX. This combination, which provides a good balance of properties,assumes a normal rimmed steel electrode core wire, essentially free oftitanium.

TABLE. [X

case titanium in the core should be substituted for the quantities ofmetallic titanium specified in the coating of our improved electrodes.

Directions have been given for determining how much titanium must beadded to highly basic limefluoride electrodes of our invention toproduce optimum deposit impact strength at low temperatures. The cleanermore purified weld deposit produced with our invention derives optimumbenefit from a titanium content of about 0.016 percent if the titaniumin the electrode is present in oxide form, of about 0.004 percent if thetitanium in the electrode is present in metallic form, and ofintermediate value if both forms are present. The deposits of Examples5, 6 and 7 herein had titanium contents of 0.024 percent, 0.02 percentand 0.003 percent respectively. Directions have also been given forfinding the maximum titanium which can be added to the improvedelectrodes of our invention before the deposit toughness falls belowthat of corresponding titanium-free base deposits. At this maximumtitanium level the deposit impact strength may still be far superior tothat of prior art deposits and at the sacrifice of some of this marginadditional titanium may be added for operational or other reasons. Thisresults in higher titanium contents in the deposit and, as has beenpointed out, the recovery of titanium is especially good for electrodeswith highly basic slags. Therefore, to prevent the abuse of ourinvention through additions of titanium which reduce the deposit impactstrength to the level of priorart electrodes, it is necessary to put arestriction on the maximum deposit titanium which is broadly about 0.07percent and preferably about 0.45

percent.

Alloy systems used' in non-austenitic weld metal deposits differamongthemselves in their inherent ranges of toughness and while our inventionhas beneficial effeet on many alloy systems it will not transform a pooralloy system into an excellent one, I

The 2- be percent chromium 1 percent molybdenum heat-treatable,stress-relievable alloy deposited by AWS E-90l8B3 class electrodes isnormally expected to be noticeably poorer in impact strength than thenickel alloyed deposits such as those produced by AWS E-ll018electrodes. The chromium-molybdenum alloys are widely used for theiradvantages in creep strength and/or resistance to graphitization, buttougher chromium-molybdenum weld deposits would be of major interest tomany users. In the past a manganese content near the top of itspermissible range has been used in most welds in order to obtain thebest possible as-welded toughness level. However, the higher manganeseresults in an appreciable drop in toughness when the weldsare subjectedto long terms stress relief, as well as rather poor toughness in thequenched and tempered condition. Low manganese deposits show lesstoughness damage on stress relief and heat treatment but are generallyof unsatisfactory toughness either as welded or as stress relieved.Improved electrodes according to our invention can often improve to anadequate level the toughness of alloy systems which are suitablemetallurgically for stress relief and/or heat treatment.

Example 8 of Table X illustrates improvements in im pact strengthattained in an AWS E-9018B3 deposit through our invention.

TABLE X Prior Art Invention Electrode description E-90l 8B3 Examglekfl le Standard example 1 but silicate alloy addition bound type changed tomeet E-90l8B3 1 chemistry Electrode slag basicity 1.48 4.42 Hardness,Rockwell "c" scale As welded 32 38 As stress relieved 27 k 24 CharpyV.-notch' after stress relief (1 hr at 1275 R), ft-lbs Room temperature52 172 0 F. l 1 118+ Deposit Chemistry, Carbon 0.060 0.1 10 Manganese0.71 0.70 Silicon 0.67 0.35 Chromium 2.20 2.35 Molybdenum 0.98 0.77Sulfur 0.016 0.0045 Titanium 0.045" 0.045"

d derived from alloy recovery curves We have no fully satisfactoryexplanation of why the impact properties of deposits produced accordingto our invention are so much better than those-that have been availablein the past. It has been shown that the sulfur level is important in'wrought non-austenitic steels of intermediate and higher strength. Allother factors being the same, major improvements in impact strength canbe made if the sulfur is reduced to very low levels, below 0.01 percent.One of the reasons our basic slag is so beneficial would seem to berelated to its ability to desulfurize steels. A welding slag with abasicity of about four will typically reduce the deposit sulfur levelfrom a 0.025 percent sulfur core wire to below 0.01 percent sulfur. Thisability to desulfurize is certainly beneficial, and must aid inobtaining good impact strength, yet it does not seem to be the fullexplanation of our good results. Coatings which produce high aluminaslags are also very effective desulfurizers, and we have made many whichhave reduced the deposit sulfur level to the range 0.002 percent to0.004 percent, yet these do not show the unprecedentedly good impactproperties of the deposits made according to our invention. Similarly,conventional E-XXlS coatings are desulfurizing, although to a lesserextent, and when-applied to low sulfurcorc wires containing 0.005percent to 0.008 percent sulfur they can provide deposits containingonly 0.002 percent to 0.004 percent sulfur, yet these deposits, whilethey have good impact strength, are not nearly as tough as deposits madein accordance with our invention. 1

It has also been proposed that the high oxygen content of coveredelectrode welds is the major damaging factor to deposit toughness, sinceOxygen is known to severely damage the impact strength of wroughtmaterials. Analyses of conventional manual lime-fluoride electrodedeposits show oxygen levels in the range of from 200 to 450 ppm. Loweroxygen levels are obtained with our invention, from 130 to 190 ppm, butwhen comparing pairs the better deposit often has a higher oxygencontent. Thus again, while a general relationship exists and loweroxygen is undoubtedly beneficial, oxygen isnot the,full explanation. Inwrought steels, 130 to 190 ppm would be very detrimental to impactproperties.

Our invention permits the use of inexpensive commercial quality corewires instead of very expensive high purity core wires. To illustrate,an electrode for producing weld deposits matching the low temperatureimpact properties of 9 percent nickel steel has been.

sought for years; a bare high purity wire for gas metal arc use has beenreported, but it is very expensive, and even with the best and highestpriced practices to control impurities the ability to deliver a minimumCharpy V-notch deposit impact strength of 25 ft-lbs at 320 F. is notassured. However, in a series of eight tests alloyed electrodesaccording to our invention were made with two high purity vacuum meltedcore wires and six low carbon commercial core wires so that each wouldproduce a 9 percent nickel weld deposit. At 320 F. the Charpy V-notchimpact values of the deposits ranged from 42 to 47 ft-lbs; nosignificant difference was found between those-made using electrodeswith the high purity high priced core wires and those made usingelectrodes with commercial quality core wires.

When conventional coatings were used with the low priced wires thedeposits were so poor in toughness that they were not worth considering,and even with the high priced wires conventional coatings did notproduce satisfactory deposits.

Of the electrodes cited in Table IV, the electrode of our invention wasmade with a commercial C1008 mild steel core wire containing 0.007percent phosphorous and 0.02 percent sulfur, while the typical prior artelectrodes were made with higher-cost higher-purity electric furnacecore wires containing 0.01 percent max. phosphorous and 0.01 percentmax. sulfur, typically containing around 0.006 percent of each element.Both wires result in a deposit with about 0.005 percent phosphorous and0.004 percent sulfur.

While we have described certain present preferred methods of practicingthe invention, it is to be distinctly understood that the invention isnot limited thereto but may be otherwise variously embodied andpracticed within the scope of the following claims.

We claim: I

l. A method of producing an improved nonaustenitic steel weld depositcharacterized by superior toughness in the Charpy V-notch impact test bymelting a covered ferrous low hydrogen arc welding electrode consistingof a current conductive core and a lime-fluoride coating, which methodconsists of (l) proportioning the core and coating components containingmetallic and oxide forms of the basic metals of the group consisting oflithium, sodium, potassium, cesium, magnesium, calcium, strontium andbarium and of the acid metals of the group consisting of aluminum andsilicon so that when all components are melted together under theinfluence of an electric welding are they produce a weld metal depositand a welding slag with a basicity or mole ration of oxide of basicmetal to oxide of acid metal of at least 2.2 and restricting sources ofmetallic and oxide forms of titanium in the core and coating componentsso that the weld metal deposit contains less than 0.07 percent titanium,(2) establishing an electric arc and (3) melting the core and coatingunder the influence of the electric arc whereby to produce a weld metaldeposit and a welding slag.

2. A method as claimed in claim 1 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in themetallic form.

3. A method as claimed in claim 1 in which the basicity of the producedwelding slag is at least three.

4. A method as claimed in claim 3 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in metallicform.

5. A method as claimed in claim 3 which the produced deposit containsless than 0.045 percent titanium.

6. A method as claimed in claim 5 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in metallicform.

7. A method as claimed in claim 1 in which the electrode containstitanium-bearing components selected from metallic and oxide forms oftitanium in such quantity that the maximum value for the expressionpercent electrode titanium as oxide present in the coating 2.6 timespercent electrode titanium as metal present in the coating is related tothe welding slag basicity according to the following schedule: 1.71percent for a basicity of less than 3, 1.18 percent for a basicity of 3to 4 and 0.89 for a basicity of over 4.

8. A method as claimed in claim 7 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in metallicform.

9. A method as claimed in claim 7 in which the basicity of the producedwelding slag is at least 3.

10. A method as claimed in claim 9 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in metallicform.

11. A method as claimed in claim 7 in which the produced depositcontains less than 0.045 percent titanium.

12. A method as claimed in claim 8 in which the current conductive corecomprises a mild steel wire.

13. A method as claimed in claim 1 in which the electrode containstitanium-bearing components selected from metallic and oxide forms oftitanium in such quantity that the ratio (percent electrode titanium asoxide present in the coating 11 times percent electrode titanium asmetal present in the coating/percent electrode CO present in thecoating) has a value of 0.04 to 0.13.

14. A method as claimed in claim 13 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in metallicform.

15. A method as claimed in claim 13 in which the basicity of theproduced welding slag is at least 3.

16. A method as claimed in claim 14 in which the basicity of theproduced welding slag is at least 3.

17. A method as claimed in claim 13 in which the produced depositcontains less than 0.045 percent titanium.

18. A method as claimed in claim 13 in which the current conductive corecomprises a mild steel wire.

2. A method as claimed in claim 1 in which the electrode containsdeoxidizer metal, said deoxidizer metal comprising magnesium in themetallic form.
 3. A method as claimed in claim 1 in which the basicityof the produced welding slag is at least three.
 4. A method as claimedin claim 3 in which the electrode contains deoxidizer metal, saiddeoxidizer metal comprising magnesium in metallic form.
 5. A method asclaimed in claim 3 which the produced deposit contains less than 0.045percent titanium.
 6. A method as claimed in claim 5 in which theelectrode contains deoxidizer metal, said deoxidizer metal comprisingmagnesium in metallic form.
 7. A method as claimed in claim 1 in whichthe electrode contains titanium-bearing components selected frommetallic and oxide forms of titanium in such quantity that the maximumvalue for the expression percent electrode titanium as oxide present inthe coating + 2.6 times percent electrode titanium as metal present inthe coating is related to the welding slag basicity according to thefollowing schedule: 1.71 percent for a basicity of less than 3, 1.18percent for a basicity of 3 to 4 and 0.89 for a basicity of over
 4. 8. Amethod as claimed in claim 7 in which the electrode contains deoxidizermetal, said deoxidizer metal comprising magnesium in metallic form.
 9. Amethod as claimed in claim 7 in which the basicity of the producedwelding slag is at least
 3. 10. A method as claimed in claim 9 in whichthe electrode contains deoxidizer metal, said deoxidizer metalcomprising magnesium in metallic form.
 11. A method as claimed in claim7 in which the produced deposit contains less than 0.045 percenttitanium.
 12. A method as claimed in claim 8 in which the currentconductive core comprises a mild steel wire.
 13. A method as claimed inclaim 1 in which the electrode contains titanium-bearing componentsselected from metallic and oxide forms of titanium in such quantity thatthe ratio (percent electrode titanium as oxide present in the coating +11 times percent electrode titanium as metal present in thecoating/percent electrode CO2 present in the coating) has a value of0.04 to 0.13.
 14. A method as claimed in claim 13 in which the electrodecontains deoxidizer metal, said deoxidizer metal comprising magnesium inmetallic form.
 15. A method as claimed in claim 13 in which the basicityof the produced welding slag is at least
 3. 16. A method as claimed inclaim 14 in which the basicity of the produced welding slag is at least3.
 17. A method as claimed in claim 13 in which the produced depositcontains less than 0.045 percent titanium.
 18. A method as claimed inclaim 13 in which the current conductive core comprises a mild steelwire.